This invention generally relates to the manufacture of integrated circuits (IC""s), hybrid systems, and more specifically, to the packaging thereof.
A common practice in the packaging of IC""s (integrated circuits) is to mount the IC die (chip) onto a header which electrically connects the pads of the chip to complete the electrical connection to the socket pins. This assembly is then encapsulated in a plastic potting compound such as epoxy. In some cases, epoxies are used to adhere the lid to the base of an IC body. However, moderately high temperatures may cause this epoxy to release gaseous products which may damage the IC. Moisture coupled with internal IC materials has been a cause of catastrophic failure in some IC and hybrid systems. In the industry, an epoxy seal is generally considered not to be hermetic, since epoxies may gradually leak gaseous products from the surrounding atmosphere into the IC.
An alternative to plastic packaging is hermetic packaging. Some IC""s and hybrid systems do not permit plastic encapsulation because of the application environment; for example, military standards for hermetic packages typically dictate that the seal material be metal. One type of hermetic seal in the prior art comprises an alumina ceramic base with printed wiring connections to electrically connect the package pins to the pad connections of the IC chip. The chip is surrounded by a suitable metal ring body, such as xe2x80x9cKovarxe2x80x9d, which is hermetically sealed to the ceramic base. A lid is then hermetically sealed to this metal body. The hermetic sealing operation requires high temperatures to seal the lid to the body while at the same time providing an internal inert gaseous atmosphere. Another type of package is ceramic with plated metal seal (e.g. W, Ni and Au) surfaces on the upper edge of the base and on the lower edge of the lid. Solders (e.g. SnPb, SnAu) are typically used to solder seal the lid to the base.
The present invention is a hermetically sealed system, comprising a base, a metal sealing member mounted on the top edge of the base, an organic sealant mounted on the top edge of the base adjacent the metal sealing member, a lid mounted on the metal sealing member and the organic sealant and a hermetically sealed cavity contained within the lid, metal sealing member and base.
The present invention also involves a method for hermetically sealing a device, comprising the steps of providing a base, applying a metal seal member along the top edge of the base, applying an organic sealant adjacent the metal seal member, covering the metal seal member and the organic sealant with a lid to create a cavity between the base, the lid and the metal seal member, compressing the metal seal member between the lid and the base to provide a hermetic seal within the cavity, and curing the organic sealant, wherein the seal is formed at room temperature.
Advantages of the present invention include providing a hermetically sealed package at economical material, labor and tool costs without the need for high sealing temperatures. The shrinkage of the organic sealant 26 during curing applies pressure to the metal seal member 28, enhancing the effectiveness of the hermetic seal.